This invention relates to sheet feeding apparatus and in particular to a sheet feeder utilizing a cassette as a supply of individual sheets and a mechanism for locating the feed rollers for feeding the sheets.
In the automatic reproducing apparatus available today, individual sheets of copy paper are separately fed through the copier and processed one at a time. In this process it is convenient to have a supply stack of sheets from which to feed the individual sheets. Modern day business desires require that a copier be capable of faithfully reproducing original documents of various sizes, configurations and on various types of copy sheet. To facilitate this operational flexibility, it has been customary to provide the supply of cut sheets in a cassette form. Typically, each cassette comprises a box like base support member with walls on all four sides to confine the cut sheets to the contained space. The base support which has an aperture in its base has a tray member supported on it so that when a lifting tongue is inserted through the aperture the leading edge of the tray member with a stack of sheets on it is lifted into feeding engagement with a pair of separator feed rolls.
Typically, an office has several such cassettes, each of which is designed to contain sheets of predetermined width and length. In feeding the sheets from the cassettes care must be taken in the location of the separator feed roller. With reproducing apparatus capable of accomodating copy sheets of several sizes, if the feed rollers are fixed they will contact the sheets to be fed at different points depending on the size of the sheet. To insure aligned feeding of sheets, substantially the same feeding forces should act on each side of a sheet being fed. To achieve this the feed rolls should be positioned such that they act on both sides of the sheet in the same way. If the action of the feed rolls is not the same on both sides of the sheet being fed, the sheets may become misaligned and cause paper jams in their path through the copier. Specifically, in a sheet feeding system using a forward buckle of the sheet over corner snubbers, if the feeding forces on both sides of the copy sheet are not the same the sheets will tend to skew in one direction eventually resulting in a jammed machine.